The uncontrolled proliferation of cancer cells is accompanied by the increase of immature cell populations. (Bloch, A., Cancer Treat. Rev. 68:199-205, 1984.) Although cancer cells are characterized by a marked capacity to proliferate and a limited capacity to differentiate under normal homeostatic conditions, experimental evidence has demonstrated that neoplastic cells can be induced to differentiate, indicating that malignant processes can be altered or, at least partially, reversed.
The retinoids are a family of compounds consisting of vitamin A, retinoic acid (RA) and related derivatives. They play a pivotal role in normal development of endodermally-, mesodermally- and ectodermally-derived tissues. (Umesono K. et al., Nature 336:262-265, 1989).
The mode of action of RA has been extensively studied. In the cytoplasm, RA binds to the cytoplasmic RA-binding protein, whose role in mediating RA effects is unclear. In the nucleus, RA binds to the RA receptors (RAR-.alpha., -.beta., -.gamma.). The RAR/RA complex binds to a specific DNA sequence, as demonstrated by electrophoretic mobility shift (Rochette-Egly et al., J. Cell. Biol. 115:535-545, 1991), leading to transcription of RA target genes. RAR-.alpha. has been shown to be involved with growth and differentiation of myeloid cells in vitro. For instance, patients with acute promyelocytic leukemia have a characteristic (15:17) translocation with the breakpoint in the region of RAR-.alpha. coding sequence. Thus, mRNA for RAR are a useful tool to study potential anti-tumor drugs.
RA was reported to induce differentiation and arrest proliferation in a wide spectrum of cancer cells in vitro and in vivo, including patients with leukemia, myelodysplastic syndromes and solid tumors. For instance, Collins et al. Int. J. Cancer 25:213-218, 1980, have shown that the human promyelocytic leukemia cell line HL-60 can be induced to differentiate by RA and express cellular and molecular characteristics of granulocytes. (Umesono et al.) Emergence of differentiated features include elevated protein kinase C and intracellular lysosomal activities. Strickland et al., have shown that exposure of the teratocarcinoma cell line F9 to RA caused differentiation to visceral endoderm (Cell 15:393-403, 1978).
Several retinoids have achieved significant activity in the reversal of head and neck, skin, and cervical premalignancy and in prevention of second primary tumors associated with head and neck, skin and non-small lung cancer. Lippman et al. (J. Cell. Biochem. 22:1, 1995) have demonstrated chemoprevention activity of retinoids in aerodigestive tract carcinogenesis. This was tested in the two-stage mouse lung carcinogenesis model described by Nishimo, J. Cell. Biochem. 22:231, 1995.
Strickland et al., demonstrated that in an in vivo murine model, orally administered RA increased the survival of mice bearing F9 tumors in a dose-dependent manner (Dev. Biol. 78:76-85, 1980). The tumors of the RA-treated mice were much smaller in comparison to untreated animals and showed morphological and biochemical evidence of differentiation.
Because of the low therapeutic index of RA, its isomer, all-trans RA (ATRA), has been extensively studied. At 1 .mu.m, ATRA has been shown to cause differentiation in vitro as demonstrated by measuring an increase of nitro-blue tetrazolium (NBT) reduction (Chomienne et al., Blood 76:1710-1717, 1990).
Evidence has also accumulated for in vivo induction of differentiation by ATRA treatment. One morphological feature indicating differentiation of promyelocytic leukemia cell populations to mature cells is the appearance of Auer rods (homogenous crystallinic red-stained structure). Treatment of acute promyelocytic leukemia (APL) patients with ATRA resulted in complete remissions without bone-marrow hypoplasia. The presence of Auer rods in the maturing cells of these patients confirmed the differentiating activity of ATRA.
Due to results from clinical and laboratory studies, ATRA is now considered to be a first line therapeutic agent for promyelocytic leukemias (Wright D.G., Blood 67:334-337, 1987). However, the achievement of remission induced by ATRA tends to be brief and may be explained by rapid clearance in patients resistant to ATRA (Muindi et al. Cancer Res. 52:2138-2142, 1992). Moreover, Adamson et al. reports that patients orally administrated ATRA had highly variable absorption of the drug (J. Natl. Can. Inst., 85(12):993-996, 1993). Hence, maintenance of effective plasma concentrations and toxicity are problems associated with retinoid treatments (Adamson et al., J. Natl. Cancer Inst. 85:993-996, 1993).
Butyric acid (BA) is a non-toxic natural product. It is supplied to mammals from two main sources: 1) the diet, mainly from dairy fat, 2) as a major product of bacterial fermentation of unabsorbed carbohydrates in the colon, where it reaches mM concentrations (Cummings J. H., Gut 22:763-779, 1982; Leder A. et al., Cell 5:319-322, 1975).
BA has been known for nearly the last three decades to be a potent differentiating and antiproliferative agent in a wide spectra of neoplastic cells in vitro (Prasad N. K., Life Sci. 27:1351-1358, 1980). In cancer cells, BA is reported to induce cellular and biochemical changes, e.g., in cell morphology, enzyme activity, receptor expression and cell-surface antigens (Nordenberg J. et al., Exp. Cell Res. 162:77-85, 1986; Nordenberg J. et al., Br. J. Cancer 56:493-497, 1987; and Fishman P. H. et al., J. Biol. Chem. 254:4342-4344, 1979).
Although BA or its sodium salt (sodium butyrate, SB) has been the subject of numerous studies, its mode of action is unclear. The most specific effect of butyric acid is inhibition of nuclear deacetylase(s), resulting in hyper acetylation of histones H3 and H4 (Riggs M. G., et al., Nature 263:462-464, 1977). Increased histone acetylation, following treatment with BA has been correlated with changes in transcriptional activity and the differentiated state of cells (Thorne A. W. et al., Eur. J. Biochem. 193:701-713, 1990). BA also exerts other nuclear actions, including modifications in the extent of phosphorylation (Boffa L. C. et al., J. Biol. Chem. 256:9612-9621, 1981) and methylation (Haan J. B. et al., Cancer Res. 46:713-716, 1986). Other cellular organelles, e.g., cytoskeleton and membrane composition and function, have been shown to be affected by BA (Bourgeade M. F. et al., J. Interferon Res. 1:323-332, 1981). Modulations in the expression of oncogenes and suppressor genes by BA were demonstrated in several cell types. Toscani et al., reported alterations in c-myc, p53 thymidine kinase, c-fos and AP2 in 3T3 fibroblasts (Oncogene Res. 3:223-238, 1988). A decrease in the expression of c-myc and H-ras oncogenes in B16 melanoma and in c-myc in HL-60 promyelocytic leukemia were also reported (Prasad K. N. et al., Biochem. Cell Biol. 68:1250-1255, 1992; and Rabizadeh E. et al., FEBS Lett. 328:225-229, 1993). However, BA is normally metabolized rapidly and has a very short half-life in vivo, thus the achievement and maintenance of effective plasma concentrations are also problems associated with BA.
Apoptosis is the physiological mechanism for the elimination of cells in a controlled and timely manner. Organisms maintain a delicate balance between cell proliferation and cell death, which when disrupted can tip the balance between cancer, in the case of over accumulation of cells, and degenerative diseases, in the case of premature cell losses. Hence, inhibition of apoptosis can contribute to tumor growth and promote progression of neoplastic conditions. BA is known to induce cell death via apoptosis.
Synergistic anti-proliferative and differentiating effects of combinations of RA with other differentiating agents or cytokines have been suggested. For instance, Breitman et al., demonstrated that BA alone induced differentiation of HL-60 cells, a human promyelocytic cell line, with an ED50 of 444 .mu.M, and RA alone induced HL-60 cells with an ED50 at 0.13 .mu.M. However, the combination of about 28 nM RA with BA reduced the ED50 value for BA from about 400 to about 75 .mu.M, a dose reduction index value of about 6-fold (Cancer Res. 50:6268-6273, 1990). Based on his study, Breitman suggested that RA might be useful in combination with other agents in the treatment of some leukemias. However, treatment with either BA or RA alone or in combination will continue to have the problems of toxicity, as well as achieving and maintaining effective plasma concentrations.
Others have studied conjugated RA compounds. For instance, Parish, U.S. Pat. No. 4,677,120 (issued Jun. 30, 1987) and PCT Application No. WO 90/06751 disclose the use of compounds of formulas A or B: ##STR2## wherein R is CR.sub.2 '"OC(.dbd.O)CR.sub.3 ', R' is H or C.sub.1 -C.sub.6 alkyl, R'" is R' or the hydrocarbon backbone of fatty acids, for affecting the reduction and reversal of photo aging and skin cancer. This application does not disclose or enable methods of the present invention.
Gross, U.S. Pat. No. 4,900,478 (issued Feb. 13, 1990), discloses, inter alia, all-trans-9-4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nona-tet raenoic acid and in EPO Application 0449099 discloses the use of compounds of the formula R.sup.1 OCH(R.sup.2)OC(O)R.sup.3, wherein R.sup.1 is 13-cis-retinoyl, R.sup.2 is alkyl and R.sup.3 is alkyl or alkoxy, for the treatment of skin disorders. This application does not disclose or enable methods of the present invention.
Thus, there remains the need to identify compounds as effective as the combination of BA and RA as differentiating or anti-proliferating agents for the treatment of cancers. Such compounds need to have high potency without the problems associated with BA and RA.
This invention addresses this need and is thus directed to the novel compounds of Formula (I) and, in particular, to retinoyloxymethylbutyrate (ROBA), which are more potent than BA or RA alone or combined, to compositions comprising same and to methods of using same for the treatment of cancers and other proliferative diseases, for gastrointestinal disorders, for ameliorating wrinkles, and for wound healing. None of the references discussed above teach or suggest the compounds of Formula (I), pharmaceutical compositions containing same or the methods of using said compounds or compositions as anti-cancer and anti-proliferative agents.